Porcelain enameling



Patented Mar. 2, 1,954

PORCELAIN ENAMELING Le Roy L. Moss, Cleveland, Ohio, assignor to Ferro Corporation, a corporation of Ohio No Drawing. Application May 14, 1951, Serial No. 226,273

Claims. (Cl. 106-48) This invention relates as indicated to porcelain enameling and has more particular reference to dry-milled enamels and to a process for producing the same.

In the present day practice of dry-milling porcelain enamel, the frit is placed in a dry mill with grinding balls and then ground until about 97% passes through a 200 mesh sieve. This finely ground material is then either fired directly on cast iron (dry process) or it is blunged with water, clay, salts etc. and then applied to sheet steel (wet process).

Porcelain enamels bearing antimony or zirconia as the opacifying agent when used in dry-milling applications are particularly troublesome. These enamels when dry-ground and applied by either the wet or dry process and then fired onto a work piece cause the finished piece to be disfigured by the presence of minute black specks scattered throughout the surface.

It is, therefore, the principal object of this invention to provide a process whereby dry-milled antimony and zirconia porcelain enamels will produce a surface on a work piece which is substantially entirely free of black specks.

Other objects will become apparent as the de scription proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

Broadly stated this invention comprises the process of producing dry-milled porcelain enamel frits which upon subsequent firing onto a work piece are substantially free of black specks which comprises charging a mill with a frit selected from the class consisting of antimony-opacified frits or zirconia-opacified frits, adding a minor amount of a carbon dioxide-absorbing agent and milling said frit and carbon dioxide-absorbing agent.

After extensive study I have evolved the theory that black specks develop on dry-milling because of carbon dioxide pick-up of the finely divided material in the presence of moisture. I have found that by adding small amounts of such carbon dioxide-absorbing agents as the hydroxto about 0.3%

black-specking when fired on a work piece. I have also found that various commercial carbon dioxide-absorbing agents such as Garoxite and Ascarite function efiiciently in the prevention of black-speaking in the porcelain enamels. These commercial carbon dioxide-absorbing agents are substantially sodium hydrate admixedv with asbestos.

I have also discovered that, while the carbon dioxide-absorbing agents'prevent black-specking.

the addition of small amounts of a water-repellant, such as the General Electric Dri-Films which are organochlorosilanes, enhance the lasting effects of the COz-absorbing'agent. I have found that by adding from about 0.025% to about 0.3% of methylchlorosilane in addition to the,

Goa-absorbing agent the milled porcelain enamel can be left to stand for long periods without picking up moisture and therefore will not black speck when fired on a work piece.

It is to be noted that while the Cos-absorbing agents function alone to prevent black-specking the water-repellant agent alone will not prevent the black-speaking.

In the preferred embodiment of my invention I use from about y to about 2% COz-absorbing agents per 100 parts of frit and from about 0.025 of an organochlorosilane per 100.

parts of frit.

When I refer to an antimony or a zirconiaopacified-frit I am referring to a frit to which the antimony and zirconia have been added as a .smelter addition. The following formulae are ides of sodium, potassium and magnesium to the typical examples of what is meant by frits which contain antimony and zirconia as the opacifying agents. These formulae are just two examples of many possible variations which exist. However, any formulations which contain antimony and zirconia as the opacifying agents are applicable to the present invention.

I. Antimony-opacificd formula Barium carbonate 42 11. Zirconia-opacified formula Of course my invention works equally well where antimony and zirconia have beenaddedto. the mill besides being present as smelter components.

A typical procedure in following" the process of my invention would be to add about 1% of magnesium hydroxide and about 0.125% on an organochlorosilane per 100 parts of antimony or zirconia-opacified frit to a dry mill and then grinding until at least 60% of the frit passes through a 200 meshsieve. It?iSTtOkbEI'IOtGdihEt the final particle size of the milledifrit is deter--- mined by its end use; Thatiswhetherit is to be used on castiro'nor sheet steel or used as a dry process application or a wet processiapplica tion. Those skilled: in: the art will readily recognizethe properparticle size according to their use and method of application.v

Other modes of applying: the: principle oi the inventionmay be employed provided the features stated in anyof the following claims or the equivalent of suchlbe employed;

I-therefore particularly: pointout-'artd' distinct lyclaim as my 'inventiom 1 The method-50f producing dry m'illed' porcelain enamels .frits:- which upon subsequentfiring onto a workpiece aresubstantialiyyfr'ee of bla-cic specks which comprises: charginga mill: with a frit selected from: the? class consisting of antimony-opacified and zirconia opacifiedr irits adding from: about V3 to about12 per 100 parts: of; said: fritf ofas carhomdioxideeab'sorbing agent and then milling saidtmixtu-reaurrtiliat least 60% of said mixture passes throug-lra zflormeshf SlfiVBi.

21: The method of'producing:'dry milledpnrca la-in:.tenamels: fritszwhichruporr subsequent onto 'arwork. piece are substantially free ofiblack specks which comprises charging a mill witlma frit; selected:- from: the class consisting of antimony-opacified and: zirconia-opacifi'ed frits;

adding: from: about /8'%"tU" about 2%-pjer: 100

parts'of said :frit of a carbon dioxid'eeabsorbing; agent and fromwabout :025%Lto about0.3% of an organochlorcsilaneand then milling-said mix ture until at least 60% of saidgm'ixture passes through a: 200 mesh sieve:

3. Thei. method of producing dry-milled por celain' enamels. -frits-which upon subsequent fir-- ing onto a work: piece are substantiallyrfree'of;

black specks which comprises charging a mill with a frit selected from: the class'consisting of antimony-opacified and zirconia-opacified frits adding from about to about 2% per 100 pants-of saidfrit of somum-hydroxide and from about 0.025% toabout 0.3% ofan organoehl'oi o silane and then milling said mixture until at least 60% of said mixture passes through a 200 mesh sieve.

4. The method of producing dry-milled porcelain enamels frits which upon subsequent firing onto a work piece are substantially free of black specks which comprises charging a mill with a frit selected from the class consisting of antimony-opacified and vzirconia-opacified frits adding from about to about 2% per 100 parts of said frit of potassium hydroxide and from about 0.025% to about 0.3% of an organechiorosilane and then milling said mixture until at least 60% of said mixture passes through a 200 mesh sieve.

The method? of producing dry-milled porcela'ir'r enamels frits which upon subsequent firing onto 'awork piece are substantially free or black-specks which comprises charging a mill with a frit selected from the class consisting of antimony-'opacified and zirconia-opacified frits adding from about ,45% to about 2% per arts of" Saidfrit of magnesium? hydroxide and from about0l025% to about 0.3% of ari-or'g'ario chloro's'ilane and then milling" saidmixture" un: til at least 60% of said mixture passes through a 200 rhesh-sie've.

6. A new" composition of matter comprisinga' dry-milled fr'it selected froiii the classof antimony and zirconia-opacified f 'ts'; and min about-$4370 to ebout 2% ofa carbb'ri dioxide-ab sorbingagent' per l00 parts friti *KA- new co'mposition of matter 'cornprising a dry-milled frit selected from the' class of antimony-opaeifiedand ween e-o ta ned frits from about /8% to-'about'-2'%- o'f acarbon clioxida" absorbing per 1 00 parts frit and from about- 0.025 to about 0. 3% ofari organochlo'ros'ila-ne per 100 parts-flit 8. A new com-position of' matter comprising a dry m-illed' frit selected front the class of from-about /8"% to about 2% of sodium hydroxide p'er'l'OO partsiritand-iroifiiabout 0.025% to about 03% of an organochloi'osilaneper 100 parts 9. A new compositionofmattr ctmpnsmg a dry-rnilie'si frit selected from the" class of antimony-opacified and zirconi'ai-iopacified frills" dro-xide-per 100 parts frit ahdfrorn about 0;02 5% to about0l3%' of-'an*orgahochlorosilaiie pei-IOD' parts rm;

10$ A" new composition of matter comprising dry-milfed"- frit' selected from" the class of antimonympacifiecl or zirconiafopacified" frits 

1. THE METHOD OF PRODUCING DRY-MILLED PORCELAIN ENAMELS FRITS WHICH UPON SUBSEQUENT FIRING ONTO A WORK PIECE ARE SUBSTANTIALLY FREE OF BLACK SPEAKS WHICH COMPRISES CHARGING A MILL WITH A FRIT SELECTED FROM THE CLASS CONSISTING OF ANTIMONY-OPACIFIED AND ZIRCONIA-OPACIFIED FRITS ADDING FROM ABOUT 1/8% TO ABOUT 2% PER 100 PARTS OF SAID FRIT OF A CARBON DIOXIDE-ABSORBING AGENT AND THEN MILLING SAID MIXTURE UNTIL AT LEAST 60% OF SAID MIXTURE PASSES THROUGH A 200 MESH SIEVE. 